Innovative Electromagnetic Surface-Controlled Subsurface Safety Valve for Immediate Securing of Well with a Damaged Control-line

摘要

A common cause of failure with surface-controlled, subsurface safety valves (SC-SSSV) is a defect in the down-hole hydraulic line, which controls the valve from the surface. Such a failure generates production losses and requires the intervention of a costly workover rig - usually not immediately available. In order to alleviate this type of situation, a "fail-safe" safety system based on electromagnetic waves (EM) was developed in order to communicate with Downhole Safety Valves (DHSV) without the need for a physical control-line. The surface emitter continuously sends a signal (low frequency) to the SC-SSSV downhole. Both items are designed to be fail-safe. The normally-closed valve remains open while receiving the signal and closes as soon as the signal is lost. This innovative "control-line free" Wireline-Retrievable SC-SSSV can be set in any landing nipple profile or anywhere in the tubing using monobore lock technology without a workover or well head modification. The primary application is to secure wells with a damaged control-line (blocked or leaking), a damaged SC-SSSV landing nipple, or wells completed without an SC-SSSV. It provides an immediate cost-effective solution - allowing production to resume with a surface-controllable safety barrier while avoiding or postponing a costly workover. A pilot installation was completed in November 2008, at the BU-HASA field onshore UAE, in a well having an SC-SSSV with control-line. An electromagnetic surface controlled wireline-retrievable DHSV was installed at a depth of 142 ft on the SC-SSSV landing nipple. The anchoring was equipped with upper and lower V-packing assemblies to isolate the existing hydraulic control line from the well. The well head was temporarily instrumented with two sensors: one pressure transducer monitoring the flow line (with adjustable thresholds) and one temperature probe connected to the surface transceiver (to detect any fire hazard) and to switch off the transceiver in the event of a problem. To transmit the EM-signal, one mono-conductor cable was directly connected from the transceiver to the well head without necessitating any well head modification or disassembly. The second cable was connected to a water well located at 50 meters from the eruptive well. The control panel was deployed in a harsh environment near an ATEX area in zone-1; thick dry sand formation did not affect the transmission of the electromagnetic signal. The downhole equipment was easily set and retrieved by a slick-line crew. The setting up of all the equipment requires no more than one day's work. Two unplanned events occurred during the three-month pilot test: a pressure gauge breakdown and a surface antenna disconnection. In both cases, the EM-signal was lost and the DHSV closed and secured the well. These functional tests, so-called "slam tests" of the downhole tool were in total compliance with the expectations of the client. Another feature, "radio silence" mode, controlled from the surface, can be useful when some other work using EM is taking place near the well head. This breakthrough slickline product has proven to be easy to install, reliable and "fail-safe". It offers new possibilities for safely and efficiently managing the countless failures of hydraulic SC-SCSSVs. Sub-standard and temporary solutions,